Final answer:
To find the inverse of a function, interchange the roles of the dependent and independent variables. The inverse function of a horizontal line is a vertical line passing through the same y-value. The restricted domain of the inverse function is the range of the original function.
Step-by-step explanation:
To find the inverse of a function, we need to interchange the roles of the dependent and independent variables. In this case, since the function is a horizontal line, all the y-values are the same. So, the inverse function will be a vertical line passing through the same y-value.
The domain of the inverse function is the range of the original function. Since the original function is a horizontal line, the range is just the single y-value. Therefore, the restricted domain of the inverse function can be written as [y-value, y-value] in interval notation.